MacOS – way to have a scheduled task that will run later if MacOSX is asleep / off at the expected runtime

macosschedule

I want a backup task to run once a week.

The computer I want to do this is a laptop, that is often off / sleeping. I would like the task to run when the computer wakes, if the computer was asleep when it was supposed to run.

Otherwise the chance of anything actually getting backed up is pretty slim.

Is there an application or MacOSX feature that does this?

My understanding of cron jobs is that if the computer is not on when it's supposed to run they will not get run on awakening, so that doesn't look like what I want.

Best Answer

There are various mechanisms in Mac OS X to do scheduled tasks. They take a little bit of effort to configure, but this page (formerly elsewhere) explains it and has links to more info. The at service, which was a bit easier to use, is deprecated as it wastes battery, and is no longer enabled by default.

The main recommendation now is to create a launchd plist, although cron is still supported.

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MacOS – How to mount disks via cron in Mountain Lion

I had this same problem and found that I could get it to work if the cron job was launched under root.

This Apple discussion link has this note:

[...] Basically, Apple is tracking where an application launches from, and seems to be preventing processes that launch from "cron" (one of the system schedulers), even indirectly, from mounting local disk volumes, even when that application is signed.

MacOS – Lauchd – Run task multiple times between time interval

You can print the StartCalendarInterval dictionaries with something like this: for h in {0..4}; do for m in {0,15,30,45}; do echo "<dict><key>Hour</key><integer>$h</integer><key>Minute</key><integer>$m</integer><key>Second</key><integer>0</integer></dict>"; done; done.

You could also run the script every 15 minutes but exit it depending on the time:

h=$(date +%-H)
m=$(date +%-M)
[[ $h -gt 4 || $h -eq 4 && $m -ne 0 ]] && exit

Or run EDITOR=nano crontab -e and add a line like */15 0-4 * * * ~/bin/script.

Best Answer

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MacOS – How to mount disks via cron in Mountain Lion

MacOS – Lauchd – Run task multiple times between time interval

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